The present disclosure relates to an image forming apparatus that includes a discharge unit for discharging a sheet member after image formation to outside from a sheet discharge port.
There is known an image forming apparatus that performs image formation based on the electrophotography. The image forming apparatus includes a fixing device and a discharge unit. The fixing device fixes a toner image that has been transferred to a surface of a sheet member such as a print sheet, to the sheet member by causing the toner image to fuse. The discharge unit is disposed more in the downstream side in the sheet member conveyance direction than the fixing device. The discharge unit includes a discharge path inside, and the sheet member to which the toner image has been fixed passes through the discharge path and is discharged from a predetermined sheet discharge port to an external tray.
In this type of image forming apparatus, an electric field is generated between a sheet member and a photoconductor drum, and a potential difference in the electric field is used for the toner image to be transferred from the photoconductor drum to the sheet member. At this time, the sheet member is put in the electric field, and electric charges of positive or negative polarity are generated on the sheet member. In addition, while the sheet member is conveyed in a conveyance path, electric charges of positive or negative polarity are generated on the sheet member due to a friction between the sheet member and a conveyance guide surface. The phenomenon in which electric charges are generated on an object is called charging. When a sheet member such as a print sheet that is made of an insulator is charged, the generated charges do not flow, but are accumulated on the sheet member as static electricity. The sheet member contacts the conveyance guide surface and receives friction therefrom until immediately before being discharged from the sheet discharge port. As a result, the amount of static electricity charged on the sheet member becomes the largest immediately before the sheet member is discharged from the sheet discharge port. For this reason, conventionally, an electricity removing member, such as an electricity removing brush, is provided near the sheet discharge port, wherein the electricity removing member removes static electricity from the sheet member.
In addition, some conventional image forming apparatuses include a pressing member for giving stiffness (also called “toughness” or “rigidity”) to the sheet member before it is discharged. The pressing member is provided in the discharge path in the discharge unit. Specifically, the pressing member is provided near a discharge roller in the discharge path. The pressing member curves the sheet member by contacting and pressing the sheet member. With this configuration, the sheet member is stiffened when it is discharged, and thereby the sheet member is prevented from hanging down immediately after the discharge.
In addition, conventionally, there has been known a frame configuration for ensuring the rigidity of the image forming apparatus while realizing the downsizing thereof. Conventionally, reduction of the image forming apparatus in size and cost has been demanded, and downsizing of the discharge unit has been promoted. On the other hand, upsizing of the sheet member on which an image can be formed by the image forming apparatus is desired. In recent years, an image forming apparatus that can form an image on a sheet member of A3 size has been known.